The present invention relates to an apparatus which is used to retain spinal elements, such as vertebrae, in a desired spatial relationship.
A known apparatus for retaining vertebrae in a desired spatial relationship is disclosed in U.S. Pat. No. 4,648,388. The apparatus includes a plurality of threaded fasteners which are connected with vertebrae of a human spinal column. Retaining rods are bent to a configuration which is a function of the desired spatial relationship between vertebrae of the spinal column. After a rod has been bent to the desired configuration, it is inserted into clamps connected with the fasteners. The clamps are then engaged to hold the vertebrae against movement relative to the rod. Other known apparatus for retaining vertebrae in a desired spatial relationship are disclosed in U.S. Pat. Nos. 4,611,581; 4,655,199; and 4,887,595.
The prior art devices are difficult to use for retaining cervical vertebrae of the spinal column in a desired spatial relationship. Due to the structure of the cervical vertebrae, fasteners must extend into the cervical vertebrae and relative to the rod in directions that the prior art devices do not readily permit.